Field of the Invention
The present invention relates to wireless communication and, more particularly, to a method and apparatus for sounding in a wireless LAN (wireless local area network, WLAN).
Related Art
A station (STA) supporting the Institute of Electrical and Electronics Engineers (IEEE) 802.11a standard may have a transmission rate of up to 54 MPs when transmitting data through a 20 MHz channel bandwidth in a 5 GHz frequency band based on orthogonal frequency division multiplexing (OFDM).
The STA supporting the IEEE 802.11n standard may have a transmission rate of up to 600 MPs when transmitting data through a 20 or 40 MHz channel bandwidth in a 2.4 or 5 GHz frequency band based on multiple-input and multiple-output (MIMO).
The IEEE 802.11a standard is aimed at providing a 1 Gbps or greater throughput in a medium access control (MAC) service access point (SAP) layer. A wireless local area network (WLAN) system supporting the IEEE 802.11ac standard may also referred to as a very high throughput (VHT) system. For a 1 Gbps or greater throughput in the MAC SAP layer, the VHT system may support 80/160 MHz channel bandwidths and eight spatial streams (or space-time streams). When the VHT system supports a 160 MHz channel bandwidth, up to eight spatial streams, 256-quadrature amplitude modulation (QAM), and a short guard interval (GI), an STA supporting the VHT system may have a transmission rate of up to 6.9 Gbps when transmitting data in a physical layer.
To satisfy the foregoing throughput, a plurality of VHT STAs supporting the VHT system may simultaneously transmit and receive data through the same channel in communications with an access point (AP). The VHT AP may simultaneously transmit data to the plurality of VHT STAs based on space division multiple access (SDMA) or MU-MIMO. That is, data may be simultaneously transmitted or received between the plurality of VHT STAs and the VHT AP.
Currently, with an increasing demand for high-quality multimedia transmission, unlicensed frequency bands tend to expand. Further, channel bandwidths used for the existing WLAN standard make it difficult to secure contiguous 160 MHz channel bandwidths for IEEE 802.11ac. Therefore, IEEE 802.11ac may use 160 MHz channel bandwidths of aggregated non-contiguous channels.